NXP Semiconductors LPC1768 - 0 X400 F C14 C)

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User manual Rev. 3 — 19 December 2013 27 of 841
NXP Semiconductors
UM10360
Chapter 3: LPC176x/5x System control
3.6.4 External Interrupt Polarity register (EXTPOLAR - 0x400F C14C)
In level-sensitive mode, the bits in this register select whether the corresponding pin is
high- or low-active. In edge-sensitive mode, they select whether the pin is rising- or
falling-edge sensitive. Only pins that are selected for the EINT function Only pins that are
selected for the EINT function (see Section 8.5
) and enabled in the appropriate NVIC
register) can cause interrupts from the External Interrupt function (though of course pins
selected for other functions may cause interrupts from those functions).
Note: Software should only change a bit in this register when its interrupt is
disabled in the NVIC (state readable in the ISERn/ICERn registers), and should write
the corresponding 1 to EXTINT before enabling (initializing) or re-enabling the
interrupt. An extraneous interrupt(s) could be set by changing the polarity and not
having the EXTINT cleared.
Table 11. External Interrupt Mode register (EXTMODE - address 0x400F C148) bit
description
Bit Symbol Value Description Reset
value
0 EXTMODE0 0 Level-sensitivity is selected for EINT0.0
1EINT0
is edge sensitive.
1 EXTMODE1 0 Level-sensitivity is selected for EINT1
.0
1EINT1
is edge sensitive.
2 EXTMODE2 0 Level-sensitivity is selected for EINT2
.0
1EINT2
is edge sensitive.
3 EXTMODE3 0 Level-sensitivity is selected for EINT3
.0
1EINT3
is edge sensitive.
31:4 - - Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
Table 12. External Interrupt Polarity register (EXTPOLAR - address 0x400F C14C) bit
description
Bit Symbol Value Description Reset
value
0 EXTPOLAR0 0 EINT0 is low-active or falling-edge sensitive (depending on
EXTMODE0).
0
1 EINT0
is high-active or rising-edge sensitive (depending on
EXTMODE0).
1 EXTPOLAR1 0 EINT1
is low-active or falling-edge sensitive (depending on
EXTMODE1).
0
1 EINT1
is high-active or rising-edge sensitive (depending on
EXTMODE1).
2 EXTPOLAR2 0 EINT2
is low-active or falling-edge sensitive (depending on
EXTMODE2).
0
1 EINT2
is high-active or rising-edge sensitive (depending on
EXTMODE2).